The types of clutches for controlling the electric power of a vehicle may be classified into wet, dry, cone, magnetic, and dog-tooth clutches. Recently, vehicles on which a coaxial type dual clutch is mounted have been commercially released. Such a Dual Clutch Transmission (DCT) denotes a type of transmission in which two clutches are arranged on the front side of the transmission and are selectively and continuously operated, and thus gear shift time is greatly reduced. Such a DCT is an evolution of an automated manual transmission, and has recently attracted attention owing to the advantages thereof, such as low power loss, high efficiency, and sporty driving feel based on fast gear shifting, together with the high economic efficiency of a manual transmission.
In particular, in a dry clutch, the radius of the clutch must be increased so as to increase transmission torque, but the layout of the clutch is limited and thus an increase in transmission torque is restricted. Thus, it is difficult to apply a dry clutch to high-performance vehicles or large vehicles. In contrast, a DCT using a wet multi-plate clutch is advantageous in that transmissible torque can be increased if the number of plates of the multi-plate clutch is increased so as to transmit high torque/high output engine power. At this time, the wet multi-plate clutch is controlled using oil pressure, unlike a dry clutch that controls strokes.
Development of a wet DCT hydraulic system has shown a tendency to adopt a scheme for performing line pressure control using an EOP and an accumulator, thus improving fuel efficiency. In particular, a DCT is greatly advantageous in that drivability is excellent thanks to the direct connection property of a manual transmission, and power transmission efficiency is high owing to the features of a parallel-axis gear.
However, there is a problem in that, for cooling and lubrication of a transmission, a Mechanical Oil Pump (MOP) and an EOP are simultaneously driven, and a gear is always partially immersed in oil, thus deteriorating fuel efficiency.
The foregoing is intended merely to aid in the better understanding of the background of the present disclosure, and is not intended to mean that the present disclosure falls within the purview of the related art that is already known to those skilled in the art.